Contact for electric switches



June 26, 1962 H. A. ELLIOTT CONTACT FOR ELECTRIC SWITCHES Filed April 23, 1960 A m F FIGS INVENTOR.

HOWARD A ELLIOTT AGENT 3,041,577 CONTACT FGR ELECTRIC SWlTCI-ES Howard A. Elliott, Detroit, Mich, assignor to Essex Wire Corporation, Fort Wayne, lnd., a corporation of Michigan Filed Aug. 23, 196i), Ser. No. 51,346 4 Claims. (Cl. 339-221) This invention relates to electric switches and more particularly to electrical contacts of the type adapted to be secured to an electrical conductor and supported by the body or casing of an electric switch in fixed position for engagement by a movable contact member.

In the construction of switches, it has been found convenient to employ cylindrical contact pins frictionally held in holes or pockets formed in the switch casing. An end portion of such contact pin extending within the switch casing serves as a stationary contact, while the other end is arranged for connection to a conductor. Such contact pins have been commonly made from metal rod upon screw machines or from sheet metal formed into a ferrule.

Because the conductor attached to the contact pin is often subjected to considerable vibration and flexing, it is important that the contact pin include means for securely gripping both the wire strands of the conductor and the insulation sheath of the jacket. However, the contact pins with insulation-supporting portions which had been proposed prior to the present invention were quite long and had metal portions extending outside the switch case which for many applications had to be insulated.

It is an object of the present invention to provide a contact of the foregoing character that is shorter in length than prior constructions, that provides for an adequate mechanical and electrical connection between the contact and its associated conductor, and that may be simply and inexpensively fabricated from sheet metal stock.

This object is accomplished according to the present invention by forming a cylindrical sheet metal ferrule of substantially uniform outside diameter having a first section tightly embracing the insulation of a conductor upon which the ferrule is closed and a second section within which is folded a pair of narrow strips integrally attached to the outer end of the second section. The bared end of the conductor is disposed between and seized by the strips. To further assure a good mechanical and electrical connection between the conductor and the ferrule, the inner surfaces of the first section of the ferrule and the strips may be provided with grooves transversely to the longitudinal axis of the ferrule.

Other objects and features of the invention will be apparent from the following description and the accompanying drawing in which:

FIG. 1 is a top view of a portion of a switch with contacts embodying the features of the present invention;

FIG. 2 is an enlarged cross sectional view of the switch taken on the line 22 of FIG. 1;

FIG. 3 is a similarly enlarged plan view of the flat blank from which the contact is formed;

FIG. 4 is a plan view of the blank of FIG. 3 formed to receive a conductor; and

FIG. 5 is an end view of the formed blank shown in FIG. 4.

Referring now to the drawing, FIGS. 1 and 2 show a portion of an electric switch of the type used in turn signal devices for automobiles and includes a casing of electrical insulating material having on the bottom wall thereof a series of through bores 11. Each of the bores 11 has a portion of enlarged diameter so as to form a cavity 12 in which is located a metal contact 13. A con- Patented June 26, 1962 ice two of the contacts 13' and provide a connection betweenthese contacts and other contact parts of the switch which are not shown. mounted two movable contactrnembers 17 and 18 for engagement with, respectively, two of the contacts 13 and with the ends 16 of the metal strips 15 which are in contact with the other two contacts 13. A spring 19 of flat conductive material is compressed between the two contact members 17 and 18 to provide an electrical connection between the contact members and to urge the contact members against their respective fixed contact elements.

As shown in FIG. 3, the contacts; 13 are formed from a sheet metal blank comprising a generally rectangular body portion 20 with two narrow strips or tongues 21 at one edge. A series of parallel grooves 22 are formed on one side of the blank to extend across the full widths of the tongues 21. In the finished connector, these grooves serve to grip the stripped wire core 23 of conductor 14. The opposite side of the blank is formed with two parallel grooves 24 extending across the width of the body portion 20 for gripping engagement with the insulating sheath 25 of conductor 14. For a contact formed from .OZS-inch thick brass stock for use with No. 18 A.W.G. stranded copper wire having a .023-inoh thick Sheath of polyvinyl chloride, grooves 22 may have a depth and width each of .006 inch while grooves 24 may have a width of .016 inch and a depth within the range of .005 inch to .010 inch.

Before the contact 13 is secured to a conductor 14, tongues 21 are folded over against the side of the body portion 20 having the grooves 24 and the blank is then bent to form a generally U-shaped channel as shown in FIGS. 4 and 5 with the grooves 22 and 24 on its inner surface. It will be noted that the portion of the channel in which the tongues 21 are folded is of reduced cross sectional area to receive the stripped core 23 of the conductor 14 while the larger portion serves to receive the insulated portion of the conductor 14. When a conductor 14 with a stripped end is inserted in the channel, the contact 13 is crimped to form a ferrule of substantially circular shape as shown in FlGS. 1 and 2.

It will be observed that while the contact 13 has a, substantially uniform diameter throughout its length, the contact 13 will have two internal sections of different cross sectional areas. By selection of the proper blank thickness in respect to the conductor dimensions, crimping of the contact will result in substantial compression of both the stripped portion and the insulated portion of the conductor which assures a good mechanical and electrical connection between the contact and the conductor. Thus, a secure and durable connection is attained by a method which is suited to high production at a low cost. Because any portion of the contact may be used to frictionally retain the contact in a hole or pocket in a switch casing, the contact may be quite short and need not extend outside of the switch casing.

While the invention has been illustrated and described in its preferred embodiment and in conjunction with a particular switch, it should be understood that the invention is not to be limited to the precise details herein illustrated and described, since the same may be carried out in other ways falling within the scope of the invention as claimed. 7

What is claimed is:

1. Electrical connection means for a switch including in combination: an electrical insulating casing wall; said wall having a generally cylindrical bore formed therethrough; a generally cylindrical electrical switch contact Within the casing 10 are slidably supported in said bore by frictional engagement with insulating material bounding said bore; an insulated electrical conductor with an exposed length of conductor inserted into said contact; said contact comprising a sheet metal blank formed to provide a tubular body; said body having one end portion which embraces the insulation on said conductor; the other end portion of said body having an edge portion thereof folded back into the body forming a projection for clamping the exposed length of said conductor; said body being crimped about said conductor with said one end portion tightly embracing the insulation on said conductor andtwith said other end portion tightly embracing the, exposed length of said conductor so that said conductor is firmly embraced throughout substantially the length of said body; and said crimped body having a substantially uniform diameter throughout its length.

2. Electrical connection means according to claim 1 wherein said folded edge portion of said body comprises two narrow strips facing each other and gripping the ex: posed length of said conductor.

3. Electrical connection means according to claim 2 wherein the contiguous surfaces of said strips are provided With a series of grooves forming conductor-gripping abutments.

4. Electrical connection means according to claim 3 and further characterized by the inner surface of said one end portion of said body being provided with grooves forming insulation-gripping abutments.

References Cited in the file of this patent UNITED STATES PATENTS 1,262,155 Zimmerman Apr. 9, 1918 2,800,638 Hammell July 23, 1957 2,961,634 Elliott et a1 Nov. 22, 1960 FOREIGN PATENTS 602,636 Great Britain May 31, 1948 

